Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$151.81	10.167%	$167.2445	$167.24	$167.25	$167.20
Purchase #2	$84.25	6.256%	$89.5207	$89.52	$89.50	$89.50
Purchase #3	$50.90	6.646%	$54.2828	$54.28	$54.30	$54.30
Purchase #4	$154.90	10.353%	$170.9368	$170.94	$170.95	$170.90
Purchase #5	$26.94	3.220%	$27.8075	$27.81	$27.80	$27.80
Purchase #6	$81.46	8.643%	$88.5006	$88.50	$88.50	$88.50
Purchase #7	$166.64	4.471%	$174.0905	$174.09	$174.10	$174.10
7 purchase totals =	$716.90		$772.3834	$772.38	$772.40	$772.30